Common Name:

General Information

Aloe arborescens is an evergreen succulent shrub-like plant growing up to 5 metres tall. The stem, which is up to 30cm in diameter, branches at or near the base and is much branched above[]. Each stem is topped with a rosette of long, grey-green leaves armed with conspicuous pale teeth[].
The plant is sometimes gathered from the wild for medicines and as a local source of nectar. It is grown commercially in some areas as a medicinal plant and is frequently used for hedges and living fences. It is also commonly grown as a garden ornamental[, ].

Known Hazards

The sap of Aloe species contains anthraquinones. These compounds have several beneficial medicinal actions, particularly as a laxative, and many species of Aloe are thus employed in traditional medicine. Whilst safe in small doses and for short periods of time, anthraquinones do have potential problems if used in excess. These include congestion and irritation of the pelvic organs[]. Long term use of anthraquinone laxatives may also play a role in development of colorectal cancer as they have genotoxic potential, and tumorigenic potential[].

Botanical References

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Range

Eastern and southern Africa - Malawi, Zimbabwe, Mozambique, Botswana, S. Africa.

Habitat

Found at elevations from sea level up to 2,800 metres in montane grassland amongst rocks and in open evergreen forest, in the eastern border mountains and outliers with high local rainfall and drizzle in the dry season; also in coastal forest[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Shrub
Height	3.00 m
Pollinators	Sunbirds, Bees
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

A plant of the semi-arid to moist tropics, where it is found at elevations up to 2,000 metres. It grows best in areas where annual daytime temperatures are within the range 18 - 26°c, but can tolerate 9 - 38°c[]. It can be killed by temperatures of -1°c or lower[]. So long as the plant is not wet, it can tolerate occasional temperatures down to about -4°c[]. It prefers a mean annual rainfall in the range 400 - 1,500mm, but tolerates 300 - 1,700mm[].
Succeeds in full sun or light shade, requiring a well-drained, light to medium soil[, ]. Prefers a pH in the range 5 - 6.5, tolerating 4.2 - 7[]. Established plants are drought tolerant[].
This species hybridizes freely with several other Aloe species[].
Aloe species follow the Crassulacean acid metabolism (CAM). CAM plants can fix carbon dioxide at night and photosynthesize with closed stomata during the day, thus minimizing water loss. This, plus their succulent leaves and stems, and the presence of a thick cuticle, makes them well adapted to dry conditions[].

Edible Uses

The flowers are sucked for their sweet nectar[].

In Japan the leaves are used as a vegetable and as a health food because they are thought to overcome constipation. Parts of the stem with a number of leaves attached are marketed as a vegetable[].
The plant is an important ingredient of 'Kidachi aloe candies', a popular sweet in Japan, enjoyed for its tangy yoghurt flavour[].

Medicinal

This species is one of the main sources of Aloe for medicinal use - preparations made from it are sold as over-the-counter drugs for the acceleration of gastric secretion, as a purgative and for dermatological use[]. In Ecuador, where the plant is cultivated, it is considered the first treatment for any type of scratch, bite, or burn, and is used in hospitals as a primary treatment for burns up to the third degree[]. Worldwide attention was drawn to the possible value of the gel prepared from this and other Aloe species after the second World War, when skin burns of victims of the nuclear bombs on Japan were successfully treated with it[].
The gel of this species contains much higher concentrations of the primary compounds present in other aloes, and this higher concentration is responsible for the faster and more effective action of the gel against skin conditions[].
As in most Aloe species, the leaf exudate of this species contains anthraquinone derivatives such as aloin and hydroxyaloins[].
Although aloin is inactive as a laxative, it is activated in the digestive tract by Eubacterium species to the compound aloe-emodin anthrone, which is an effective laxative[].
Although some observations indicate that in diarrhoea induced by aloin, increased water content might be more important than stimulated peristalsis, the side effects of prolonged use point to a griping effect on the colon. Therefore, aloin should preferably be administered in combination with an antispasmodic to moderate its griping action[].
In any case, anthraquinone laxatives should not be used for longer than 8 - 10 days, or by children younger than 12 years. Contra-indications also include pregnancy, breastfeeding, intestinal inflammations and haemorrhoids[].
Possible side effects of aloin include congestion and irritation of the pelvic organs. Anthraquinone laxatives may play a role in development of colorectal cancer as they have genotoxic potential and also tumorigenic potential in rodents[].
It has been claimed that aloin is also responsible for antihistamine and anti-inflammatory activity[].
Both aloin and aloeresin B have skin-whitening activity[].
The gel contains polysaccharides and glycoproteins. Apart from mannan and glucomannan, arboran A and arboran B have been identified, which have hypoglycaemic effects. The structure-function relationship of polysaccharides from gel from different Aloe species is still subject to research. Biological activity is thought to be, at least partly, due to immunomodulating effects of these polysaccharides[].
The leaf epidermis contains lectins (aloctin A and aloctin B) that inhibit the growth of fibrosarcoma in animals. The leaf powder showed protective effects against human carcinogenesis[].
In 2002 the United States Food and Drug Administration withdrew the ‘generally recognized as safe and effective (GRASE)’ status for over-the-counter drugs based on aloe exudates[].

Aloe arborescens gel works as a synergist of neomycin sulphate in eye drops; they are useful in the treatment of inflammation and infections of the eye[].
Freeze-dried leaves have shown a 70% growth inhibition of Trichophyton mentagrophytes (one of the fungi causing athlete’s foot in humans)[].

A leaf decoction is given to women to ease childbirth[]. The leaves are eaten as a vegetable as a treatment for constipation[].
The split or crushed fresh leaves are widely used to treat burns and wounds[].

Agroforestry Uses:

The plant is frequently grown in drier areas of the tropics as a hedge and living fence[]. It makes an excellent, impenetrable hedge[]. Homesteads that have been abandoned for over a century can still be traced thanks to surviving fences[].

Other Uses

None known

Propagation

Seed - sow in a sandy, well-drained potting soil in a warm, shady position in standard seed trays. Germination takes about three weeks. Cover with a thin layer of sand (1 - 2mm), keep moist and the seedlings can be planted out in individual bags or containers as soon as they are large enough to handle[].
Stem cuttings 3 - 10cm long[]. A branch or stem can be cut off, allowed to dry for a day or so until the wound has sealed, and then planted in well-drained soil or sand. It need not be rooted in any particular place and then transplanted, but can be placed directly into its permanent place in the garden. It is important to remember not to water the cutting too heavily; overwatering may cause it to rot[].

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